How about a Westfalia poptop? you can still buy them and the "fabric"
So you might be interested in this picture gallery
of a conversion.
Westy popup fabric insert.
Vans that are still being made
is a ground up build on a van. I think you would need to join since when you click on the numbers for pics, you get a notice saying that you aren't authorized access that area.
Or you could just buy this
(but would that be too easy?)
Or you could use a method similar to the one the Apache hard sided popups used.
This is a parts list of the bed end. Here is a pdf download
for a 74 (same kind we had)
BTW, we replaced our "living hinge" with dual wire pipe heat cable and replaced the metal sleeve with RV aluminum awning rail. I did have to use a pair of vise grips to close the awning rail slightly. The "solid state" sidewalls were ABS plastic... slightly thinner than the bumpy FRP you find at Lowes/Home Depot. Just not sure how you would raise the road cover (gas struts?).
4200994 & 3390015 living hinge = heat cable
4048024 rear wall lower hinge = RV awning rail (one on each side the heat cable connects then together)
5300078 = small screw that was just big enough around to cut threads into the soft aluminum awning rail track